Plastic blow molding machines of the wheel type, such as disclosed by U.S. Pat. Nos. 3,310,834 Simpson et al, 3,764,250 Waterloo, and 3,986,807 Takegami et al, have previously included a wheel having a frame supported on a base for rotation about a horizontal axis with a plurality of mold stations mounted on the wheel frame about the rotational axis such that a pair of mold supports for respectively mounting a pair of mold portions move parallel to the rotational axis between open and closed positions of the mold. Such blow molding machines conventionally include a closing station where the mold supports move the mold portions to a closed position to enclose an extruded hot plastic parison within a mold cavity for blowing to the shape of the mold and for subsequent cooling prior to opening at an opening station after approximately 3/4 of a revolution of the wheel. Toggle and lock mechanisms which are normally spring biased have previously been cam operated to move the mold supports between the open and closed position in a manner that asymmetrically loads the wheel frame and eventually results in wear that requires maintenance.
Plastic blow molding machines of the wheel type wherein the mold supports move horizontally toward and away from each other between the open and closed positions are preferable in comparison to book-type molds that pivot between open and closed positions on a mold wheel such as disclosed by U.S. Pat. No. 3,608,015 Martelli. Such book-type molds on a wheel have more limited room in the open position to permit positioning of the parison between the open mold portions which can result in manufacturing problems.